Under the present standard of the U.S. Department of Health, Education, and Welfare, Food and Drug Administration, the terms "Mozzarella" and "Scamorza" are used interchangeably. There are two types of Mozzarella (Scamorza) cheese, namely "regular" and "low-moisture" cheese. The regular Mozzarella has a moisture content of more than 52% up to 60%, while the low-moisture Mozzarella has a moisture content above 45% but not over 52%. These two kinds of Mozzarella are also referred to as "high-moisture" and "low-moisture" Mozzarella. Mozzarella cheese prepared from whole milk must contain not less than 45% fat on a solids basis, and part-skim Mozzarella must contain not less than 30% fat up to 45%. The term "pizza cheese" as used herein refers to low-moisture Mozzarella, which may be made from either whole milk or part-skim milk. Commercially, most "pizza cheese" manufactured in the United States is part-skim low-moisture Mozzarella.
In terms of volume, the major use of pizza cheese is in the commercial manufacture of pizza. For this purpose, it is important that the cheese slice or shred readily, that the slices or shreds can be handled and applied to the pizza, and that during the high temperature baking of the pizza, the cheese slices or comminuted forms continue to lay flat, and melt without burning or blistering. These properties are also desirable when pizza cheese is used for preparing other baked Italian dishes.
Another important property of pizza cheese is referred to as "stringiness". This is the "stringy" texture which can be observed when the cheese is pulled apart. It is most noticeable when the cheese has been heated and melted, as in the preparation of pizza. Without this stringy texture, a pizza cheese is usually regarded as lacking a typical and essential characteristic.
To obtain the proper stringy character in pizza cheese, a mixed starter culture is utilized containing both "coccus" and "rod" bacteria. The coccus organism is usually S. thermophilus. The rod organism is a heat-resistant lactobacillus, which commonly is L. bulgaricus. L. helveticus can also be used, or mixtures of L. bulgaricus and L. helveticus with the S. thermophilus. Typically, the rod and coccus organisms are cultured together to form a bulk starter, which is added to the pasteurized cow's milk in the cheese vat at a level of around 1.5 to 2.5% by weight based on the milk.
Another step in the manufacture of pizza cheese is important in producing a cheese with the typical Mozzarella stringiness. This is the mixing and stretching of the cheese curd in water at an elevated temperature. In batch processing of Mozzarella, water temperatures as high as 180.degree. F. have been used for the mixing and stretching of the curd. For low-moisture Mozzarella, lower temperatures can be used with continuous mix apparatus, such as the mixer disclosed in U.S. Pat. No. 3,713,220. Typical mixer temperatures with such apparatus are 135.degree. to 155.degree. F.